CTLA4 and prostate cancer: Altogether, reduced CD4+ T cell pools and their altered viability (increased CD39 expression on CD4+ Teff cells and a compensatory increase in their proliferative capacity) and an increase in the fraction of Tregs with suppressive phenotype (increased CTLA4 and PD1 expression) indicate the presence of a systemic immune suppression in prostate cancer patients before seed implantation affecting the CD4+ T cell arm of the adaptive immune system.